Evans told The Associated Press in an interview Wednesday that he has no information suggesting a specific threat against the marathon, which was targeted in 2013.

Two bombs planted near the finish line killed three spectators and wounded more than 260 others on April 15, 2013.

Evans, an avid runner, said he's canceled his plans to run the 2016 edition of the race on April 18 so he can tend to security duties. He said he had planned to make it his 50th marathon and 19th Boston, but Tuesday's attacks in Brussels prompted him to reconsider.

Instead, he said, marathon security will be his main focus.

"I can't in my right mind go out and lace up the sneakers and run that day," he said in his office, where dozens of marathon medals decorate the walls. "We're only 3½ weeks away. My priority is here, doing my job and making sure the race goes off without any problems."

Evans did not elaborate on security precautions being taken around the 120th running of Boston, America's oldest and most celebrated footrace.

He said heightened measures used since the 2013 attacks would be in place, including stepped-up patrols by uniformed and undercover officers, a greater use of surveillance cameras and tactical units, and checkpoints for the tens of thousands of spectators lining the route.

Within hours of the Belgium bombings, Boston authorities were on the phone with the FBI as well as state and international law enforcement agencies to review threats and security plans, Evans said.

"You worry about copycats. You worry about these homegrown terrorists who are in their basement plotting something," he said. "It's a constant worry for me."

Dzhokhar Tsarnaev was sentenced to death for the 2013 marathon bombing and is being held at the Supermax federal prison in Colorado.

Tsarnaev's brother, Tamerlan, was killed in a shootout with police several days after the attacks.

Evans had run the Boston Marathon in 2013 and was soaking in a hot tub when word came of the attacks.

He hasn't run his beloved race since.

"Right from the get-go, I said it would be a game time decision" whether to run next month, Evans said. "But yesterday's attacks were troubling to me."